No brother we were colonised by the English , Spanish etc a lot of mixing in Jamaica what I am saying is this
If someone is biracial as in one parent white one black ... The are not black .
See, that is to you. See, you can have a person with two "black" parents and the person might looked "mixed" to you. What if the person is half PR and Dominican, with a very light PR mother or father, and the person is a dark as you? Are you gonna say, "You are not black?"
And actually, the American system simplifies things, don't complicate things
Here is the racial system in Colonial Mexico

Simplied version of Brazil's wide range

America had a different system in place. then you go into Jim Crow, Segregation, Octoroons/Quadroons...the South, etc. Didn't matter if you are 1/2, 1/3, quarter...in the US either you are US or you one of them---that goes both ways. Back in the day, those who could pass, did or call themselves "Portuguese"
Obama had said that when it came to catching cabs he is black...
(because that is what they see)
If he never went into politics or never was the president, if he got a speeding ticket, the officer would down 'black' for race.
biracial is just a PC term because it covers all the combos, but it came more into use because being called Mulatto seems derogatory.